1. Field of the Invention
This invention relates to a small-sized electric motor used for driving a window glass in a power window device of an automobile, for example, and more particularly to a small-sized electric motor housing a built-in circuit breaker.
2. Description of the Prior Art
Heretofore, there has been used a small-sized electric motor housing a built-in circuit breaker as shown in FIG. 5 and FIG. 6.
In the small-sized electric motor 100 shown in the figures, an armature 105 is held rotatably by a gear case 102 and a motor case 104 attached to the gear case 102 with a screw 103, and a holder base 106 is fitted between the gear case 102 and the motor case 104.
The holder base 106 is provided with a circular hole 106a for inserting a commutator 105b provided to an armature shaft 105a of the armature 105 in the center portion thereof, and resilient brush holders 108 and 109 fitted with brushes 107 to supply an electric current to the armature 105 are attached to the opposite positions around about the circular hole 106a, respectively.
The holder base 106 is also provided with holding holes 106b and 106c to hold connective terminals 110a and 110b of a circuit breaker 110 at positions away from the brush holders 108 and 109 on the outside of the circular hole 106a, and the connective terminals 110a and 110b are pressed into the holding holes 106b and 106c.
The connective terminal 110a between the connective terminals 110a and 110b is connected with an end of a wire 111 by spot welding, and another end of the wire 111 is connected to the brush holder 108 by spot welding.
Another connective terminal 110b between the connective terminals 110a and 110b is connected with an external connective wire 112 by spot welding, and another brush holder 109 is connected with another external connective wire 113 by spot welding.
In this state, supplying the predetermined power through the external connective wires 112 and 113, the electric current flows from the external connective wire 112 to another external connective wire 113 through the connective terminal 110b of the circuit breaker 110, the connective terminal 110a of the circuit breaker 110, the wire 111, the brush holder 108, the brush 107, the commutator 105b, the armature 105, the brush 107 and the brush holder 109, so that the armature shaft 105a rotates in FIG. 6. Thereby a worm wheel 114 rotates by meshing with a worm 105c formed to the armature shaft 105a, and an output shaft 115 fixed to the worm wheel 114 rotates.
If the output shaft 115 is loaded and the rotation of the output shaft 115 is restricted from one cause or another, then an overcurrent flows in the circuit breaker 110 and the electric connection between the connective terminals 110a and 110b is cut off by working of bimetal.
In this manner, the motor 100 is so structured as not to pass the overcurrent into the armature 105 and prevent the armature 105 from burning out.
However, in the abovementioned conventional small-sized electric motor 100, the circuit breaker 110 is held in the holder base 106 by pressing the connective terminals 110a and 110b into the holding holes 106b and 106c provided in the holder base 106 respectively, and the connective terminal 110a of the circuit breaker 110 is connected to the one end of the wire 111 by spot welding and another connective terminal 110b of the circuit breaker 110 is connected with the external connective wire 112 by spot welding. Therefore, there is a problem in that it is unfavorable in the cost because the assemble work requires many man-hours for connecting the respective connective terminals 110a and 110b with the one end of the wire 111 and the external connective wire 112 by spot welding after pressing the connective terminals 110a and 110b into the holding holes 106b and 106c. There is another problem in that it is difficult to assemble automatically since the positioning work of the external connective wire 112 and the wire 111 is very troublesome.